This invention relates in general to foundations for buildings and similar structures, and more particularly to an apparatus and process for shoring such foundations.
Traditional procedures for shoring building foundations are for the most part quite complex and costly in that they rely on poured concrete piers. Moreover, these procedures require considerable excavation which often damages shrubbery and lawns around the buildings at which they are installed.
U.S. Pat. No. 3,902,326 to George Langenbach discloses a less complicated and less costly process for shoring foundations, but that process presents problems of a different nature. In particular, the process involves exposing the footing at several locations along the foundation, and indeed tunneling beneath the footing, so that a jacking bracket may be installed against the bottom of the footing. Then a pier is advanced through the bracket and driven into the underlying soil with a jacking device that attaches to the bracket. When the pier encounters bedrock, the reaction force exerted through the bracket against the foundation stabilizes the foundation and indeed may be increased enough to actually lift and reposition the foundation. However, to insure that the jacking bracket seats properly against the footing, the underside of the foundation must often be chiseled flat or otherwise squared off with respect to the vertical. Indeed, an inclined seating surface on the bottom of the foundation will cause the jacking bracket to skew and perhaps slip off of the foundation when the jacking force is applied to it. Also, a skewed jacking bracket may drive the upper end of the hydraulic jacking cylinder into the foundation wall, causing the rod of the cylinder to deflect and perhaps break. Chiseling a flat surface on the underside of a foundation requires a considerable amount of skill and dexterity, considering that the work is often performed through a small hole in a basement floor without opportunity for visual inspection of the surface that is chiseled.
Even when the jacking bracket of the Langenbach patent is seated properly against the underside of the footing, high lifting forces applied through the bracket to the footing cause the footing to crumble along its outer edge, and this also causes the bracket to skew and tilt the jacking equipment toward the foundation wall. Again the jacking cylinder does not align with the pier and excessive bending stresses develop in it.
Perhaps the most convenient location at which to employ the stabilizing procedure of the Langenbach patent is in the basement of a building that is being stabilized, assuming of course that the building has a basement, for that avoids what otherwise would amount to considerable excavation at the exterior of the foundation. Even though the holes in comparison to the overall basement may be small, they still require some excavation beneath the foundation and in adjoining regions.